Rolling-element bearings of this type come into use for example in paper-making machines and in this case are often embodied as spherical roller bearings. These bearings have the advantage that (small) pivoting angles between the axes of the inner ring and of the outer ring can be compensated. The outer ring raceway in this case extends arcuately, wherein respective sections of the arc function as raceways.
In the mentioned usage—but of course also in other usages—the bearing must often be used in a damp environment, such that condensation can form, which enters into the bearing.
Such a situation is shown in FIGS. 1 and 2. The spherical roller bearing 1 includes an inner ring 2 and an outer ring 3, wherein the bearing rings are each formed one-piece. The inner ring 2 has two raceways 4 and 5 for rolling elements 8 or 9; the outer ring has corresponding raceways 6 and 7 for the rolling elements 8, 9. The rolling elements 8, 9 are held by a cage 16.
The outer ring raceways 6, 7 form sections of a spherical track, which is formed arcuately in radial section. Accordingly, the spherical contour continues uninterrupted axially between the raceways 6, 7, as can be seen in FIG. 1 and in FIG. 2.
If moisture enters into the bearing or a medium condenses in the region of the bearing, the moisture collects at the deepest point of the outer ring 3—due to the fact that the raceway surface of the outer ring continuously rises laterally up to the axial end of the outer ring 3. Until the moisture can flow away over the end sides of the outer ring 3, at least in the rest state of the bearing the moisture remains in the bearing interior, which is illustrated by the accumulated moisture 17.
Here a fluid level h is already reached with relatively little moisture, which fluid level h extends into the region of the raceways 6, 7 for the rolling elements 8, 9. Accordingly the risk exists that even with relatively little moisture the raceways can corrode.
After the idle-state of the bearing, the penetrated moisture must accordingly first be pressed back out of the bearing interior by the rolling elements, so that it can run out over the lateral side surfaces of the bearing outer ring. Up to this point, however, damage to the raceways of the outer ring has sometimes already occurred.
The condensation of moisture in the bearing accordingly leads to an idle-state-corrosion of the raceways, which negatively affects the raceways, i.e. the functional surfaces of the bearing, even with relatively small amounts of liquid. This effect can also be caused, for example, if volumes of moisture reach into the bearing interior due to washing processes.
In this way, bearing failures due to corrosion are caused relatively quickly in a disadvantageous manner. The bearing service life is accordingly reduced. The bearings also quickly become incapable of being repaired, i.e. with sufficient corrosion a repair is no longer possible; instead the bearing must be scrapped.